Window Regulator

Have had some good advice from you guys, I asked a while back about the electric windows not working, have had to get a new one.
have undone all the nuts holding the unit in place, but the bit at the very top
that goes through the window glass has me baffled as how to remove?
Do I need a special tool?
Asked on the Ducato forum no joy.
2003 Ducato 2.8JTD